1. Field of the Invention
The present invention relates to an information processing apparatus and a method for controlling a power supply of the apparatus, and more particularly to an information processing apparatus for supplying power to external devices and a method for controlling a power supply of the apparatus.
2. Description of the Related Art
Nowadays, a cellular phone has been widely used in Japan as well as in all other countries around the world. The cellular phone has now digital camera function, Internet access function and various information processing functions in addition to conventional phone function and email function, thereby significantly increasing its convenience. Accordingly, it could be predicted that the cellular phone would continue to be widely used in the future.
Further, portable electronic devices such as digital camera, PDA (Personal Digital Assistance), portable audio player, etc., have been also widely used similarly to the cellular phone.
Many of these portable electronic devices incorporate a rechargeable battery such as Lithium-ion battery and are powered by the rechargeable battery. Further, when the rechargeable battery loses its power, the battery is in many cases charged with electrical power from the commercial power supply via an AC adapter, etc., dedicated to the individual portable electronic devices.
Further, an information processing apparatus typified by a personal computer has also been widely used similarly to the portable electronic devices. The information processing apparatus has various interfaces for connection with various external devices and among these interfaces, an interface configured in accordance with an industry standard such as the USB (Trademark) (Universal Serial Bus) specification or the IEEE 1394 specification is provided in many information processing apparatuses.
Moreover, in response to the fact that an interface designed in accordance with the USB specification or the IEEE 1394 specification tends to be commonly used in an information processing apparatus, many of portable electronic devices including a cellular phone tend to be provided with an interface designed in accordance with the USB specification or the IEEE 1394 specification.
USB is positioned as an interface technology to be applied to a pair of lines that can carry out serial digital data transfer through a bi-directional serial line as well as power and ground lines through which power is supplied to external devices.
Similarly to USB, IEEE 1394 is also positioned as an interface technology to be applied to a pair of lines that can carry out serial digital data transfer and is a specification that describes a method for supplying power to external devices.
Note that power supplied via an interface that supports the interface specification such as USB and IEEE 1394 is in some cases referred to as bus electrical power.
If bus electrical power can be supplied from a personal computer, etc., through USB cables to charge the battery of a portable electronic device such as a cellular phone, a user of portable electronic device is able to enjoy great convenience because he/she has no need to bring with himself/herself an AC adapter, etc., dedicated to individual portable electronic devices.
Some references disclose a technique for charging the battery of a portable electronic device such as a cellular phone using bus electrical power through USB cables.
For example, Japanese Unexamined Patent Publication (Kokai) No. 2000-201204 discloses a cable having one end connected to a USB connector of an information processing apparatus such as a personal computer and the other end connected to a battery charge connector on a cellular phone. More specifically, the cable is for supplying bus electrical power from a USB connector provided in the information processing apparatus to the cellular phone, thereby charging the cellular phone battery.
In addition to the configuration of the battery charge cable disclosed above, Japanese Unexamined Patent Publication (Kokai) No. 2000-339067 has a feature that a voltage conversion function and an over-current protection function are provided in the middle of the cable.
Further, Japanese Unexamined Patent Publication (Kokai) No. 2004-152317 discloses a technique for efficiently utilizing capabilities enabled by the OTG (USB On-The-Go) specification, which is a supplement to the USB specification (USB specification version 2.0), to allow a user to further enjoy the convenience of charging a battery using bus electrical power through USB cables.
In more detail, the battery charge method disclosed in above Kokai No. 2000-201204 or No. 2000-339067 is to supply power in one direction only, i.e., in a direction from a host device (personal computer, etc.) to a terminal device (external device such as a cellular phone connected to a personal computer, etc.). In other words, this method provides a “one-way” battery charge function.
In contrast to the above methods, Kokai No. 2004-152317 discloses a technique for connecting two terminal devices (e.g., devices A and B) using a USB OTG cable and allowing a battery provided in the device A or an external power supply connected to the device A to charge the battery of the device B. Further, the technique includes, for example, simply changing the USB cable connection in order to allow a battery provided in the device B or an external power supply connected to the device B to charge the battery of the device A. In this manner, the technique enables one of the two devices to charge the battery of the other, thereby providing a “two-way” battery charge function.
According to the battery charge techniques disclosed in above references, it becomes possible to retrieve bus electrical power from a USB connector provided in many of nowadays information processing apparatuses and terminal devices and use the bus electrical power to charge the battery of a portable electronic device such as a cellular phone. This eliminates the need for a user to bring out an electronic device such as an AC adaptor, which is dedicated to the battery charge working, for use at his/her destination site, thereby allowing the user of a portable electronic device to enjoy great convenience.
Note that interface specifications for USB, etc., (hereinafter, an interface designed in accordance with the USB specification or the IEEE 1394 specification to be able to supply bus electrical power are referred to as a USB interface, etc.) are originally intended to unify interfaces for data communication between an information processing apparatus such as a personal computer and an external device to be connected to the apparatus. Accordingly, in general, unless an information processing apparatus itself has been activated, bus electrical power is never supplied from a USB connector, etc., provided in the information processing apparatus to the external device.
A USB interface, etc., supports the “Hot Plug” function and it is assured that a USB connector, etc., is able to operate even if the USB connector is connected via the USB interface to the information processing apparatus in operation. Accordingly, as long as the information processing apparatus is in operation, it is possible to supply bus electrical power to an external device and communicate data with the external device. However, once the information processing apparatus is turned off, bus electrical power supply to the external device is stopped.
For this reason, when a user tries to connect a portable electronic device such as a cellular phone to the information processing apparatus to charge the battery of the electronic device, the user has to keep the information processing apparatus turned on even if he/she is not using the information processing apparatus. Such an operation is not recommended for the reduction of power consumption.
Further, keeping the information processing apparatus turned on during operation of a cellular phone, etc., is not recommended for the security of the information processing apparatus and in some cases, requires that the user sits near the information processing apparatus until the battery of the phone is fully charged, making the user feel inconvenient.
Further, many of nowadays information processing apparatuses, in particular portable information processing apparatuses such as a note personal computer are equipped with a power saving function. The power saving function is to automatically turn off power supplies excluding power supplies needed for a part of electronic components of the information processing apparatus, for example, when a user does not operate a key board, etc., for a predetermined period of time.
A power saving function called a “suspend” function is, for example, to automatically turn off all of power supplies excluding a power supply needed for a main memory comprised of DRAM, etc., when a user does not operate a key board, etc., for a predetermined period of time and immediately switch back to a mode just prior to the beginning of a suspend mode based on information stored in the main memory when the user presses any key on the keyboard.
Further, a power saving function called a “hibernation” function is to store in an HDD (Hard Disk Drive) the information contained in a main memory and turn off almost all of power supplies needed for electronic components including the main memory for the purpose of saving power.
The “suspend” and “hibernation” functions, etc., are very useful in terms of saving power on the information processing apparatus, however, when a cellular phone, etc., is connected to the information processing apparatus for charging the battery of the phone, power supplies in the information processing apparatus are turned off upon automatic activation of a power saving function before the battery is fully charged, inconveniently interrupting the battery charge process at this point.
Further, it is also possible to disable the “suspend” function or “hibernation” function to preferentially charge the battery of the external device. However, in such a case, after completion of battery charge, a user has to enable again those power saving functions in a time-consuming manner.